X-y=1

$\left \{ {{x-y=1} \atop {\frac{x}{2}+ \frac{y}{4}= \frac{2x-y}{3}}} \right.$
умножим второе уравнение на 12 для избавления от дробей:
$\left \{ {{x-y=1} \atop {6x+3y= 4(2x-y)} \right. \\\left \{ {{x-y=1} \atop {6x+3y=8x-4y} \right. \\ \left \{ {{x-y=1} \atop {6x-8x+3y+4y=0} \right. \\ \left \{ {{x-y=1} \atop {-2x+7y=0} \right. \\ \left \{ {{x=1+y} \atop {-2(1+y)+7y=0} \right. \\ -2(1+y)+7y=0 \\ -2-2y+7y=0 \\ 5y=2 \\ y= \frac{2}{5} \\ \left \{ {{y=0.4 } \atop {x=1+y=1+0.4=1.4}} \right. \\ (1.4;0.4)$